The present invention relates to a treatment and disposal of a radioactive liquid waste. More particularly, the invention relates to a process for disposing of a radioactive, concentrated liquid waste containing sodium sulfate as the main component which is formed in atomic power plants, etc.
It is indispensable to reduce the volume of radioactive wastes formed in an atomic power plant and to solidify the same not only for securing a storage space in that plant but also for the retrievable storage which is one of the final disposal methods.
Processes which have been proposed for reducing the volume of the radioactive waste include one wherein a concentrated liquid waste containing Na.sub.2 SO.sub.4 as the main component formed in a BWR plant is dried and pulverized to remove water accounting for a major part of the radioactive waste and the obtained powder is pelletized. It has been confirmed that, according to this process, the volume of the final solid can be reduced to about 1/8 of that obtained in a conventional process wherein the liquid waste is solidified directly with cement. However, even this process having a great volume-reduction effect has a defect that no stable solid can be prepared with a hydraulic solidifier such as cement, since pellets mainly comprising Na.sub.2 SO.sub.4 are swollen by absorbing water from the solidifier to break the solidified body. To overcome the defect of this process, a process has been proposed wherein an alkali silicate solution is used as the solidifier in combination with a water absorbent to form stable pellets (see U.S. Pat. No. 4,505,851). Though stable, solidified pellets can be prepared by this process, it encounters another problem in the pelletization of dry powder. Under these circumstances, it has been demanded to develop a process wherein the dry powder as it is can be mixed homogeneously with the solidifier.
In typical processes for the homogeneous solidification, plastic, asphalt or inorganic material is used as the solidifier. The process wherein plastic or asphalt is used has been developed mainly for the purpose of sea disposal. However, a high cost is required of the plastic and the asphalt has a problem of an insufficient heat resistance.